Adhesive composition and structure comprising at least one layer of said composition

ABSTRACT

An adhesive composition including predominantly one or two polyamide(s) having units chosen from: at least one unit denoted A with a mean number of carbon atoms per nitrogen atom, denoted CA, ranging from 4 to 8.5, advantageously from 4 to 7; at least one unit denoted B with a mean number of carbon atoms per nitrogen atom, denoted CB, ranging from 7 to 10, advantageously from 7.5 to 9.5; at least one unit denoted C with a mean number of carbon atoms per nitrogen atom, denoted CC, ranging from 9 to 18, advantageously from 10 to 18, and to the use thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/763,381, filed on Jul. 24, 2015, which is a U.S. National Stage ofInternational Application No. PCT/EP2014/051434, filed on Jan. 24, 2014,which claims the benefit of French Application No. 1350664, filed onJan. 25, 2013. The entire contents of each of U.S. application Ser. No.14/763,381, International Application No. PCT/EP2014/051434, and FrenchApplication No. 1350664 are hereby incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The invention relates to an adhesive composition, also known as abinder, and to the use thereof for making structures for transferringand/or storing gases and fluids, such as fuels or biofuels, compressedair, and braking or cooling liquids.

The invention relates more particularly to the pipes present in anengine. These pipes may be intended, for example, for transporting fuel,especially from the tank to the engine, for the cooling circuit, for thehydraulic system, or may alternatively be intended for the airconditioning or compressed air circuit or for transporting a mixture ofurea and water. These pipes may also be included in underframeapplications.

BACKGROUND

For reasons of safety and of environmental protection, especially withthe arrival of novel biofuels, motor vehicle constructors are imposingon the pipes mentioned previously particular mechanical characteristics,and also characteristics of very low permeability and of good resistanceto the various constituents of fuels, which vary from country to country(hydrocarbons, additives, alcohols such as methanol and ethanol, thealcohols possibly being predominant components in certain cases), theengine lubrication oils and the other chemical products that may beencountered in this environment (battery acid, brake liquids, coolingliquids, metal salts such as calcium chloride or zinc chloride).

The characteristics of the specifications commonly required by motorvehicle constructors for a pipe to be considered satisfactory arecumulatively the following:

good and long-lasting adhesion between the layers, if the pipe is amultilayer pipe, most particularly after having been exposed to fuel;

good integrity of the connections (pipes+joints) after circulation offuel, i.e. not leading to any leaks;

good dimensional stability of the pipe, when it is used with gasoline;

good resistance to cold shocks (from −30° C. to −40° C. approximately),so that the pipe does not break;

good heat resistance (approximately 150° C.), so that the pipe does notbecome deformed;

good resistance to aging in a hot oxidative medium (for example: hot airof the engine compartment, from 100 to 150° C. approximately);

good resistance to fuels and to their degradation products andespecially with high contents of peroxide;

very low permeability to fuels, and more particularly good biofuelbarrier properties, as regards both its polar components (such asethanol) and its apolar components (hydrocarbons);

good flexibility of the pipe to facilitate mounting, especially of thefuel feed pipework;

good resistance to ZnCl₂ (for example in winter, when roads are gritted,the exterior of the pipe being exposed to this environment).

Furthermore, the desired pipes must avoid the following drawbacks:

if the pipe is a multilayer pipe, peeling of the layers, especially theinner layers, especially during the insertion of a joint (which may leadto leaks);

excessive swelling of the pipe after aging in gasoline/diesel systems(including for biodiesels or biofuels), which may lead to leaks orproblems of positioning under the vehicle.

At the present time, two types of pipe exist, monolayer and multilayerpipes, i.e., pipes consisting of one or more layers of polymer.

Conventionally, the pipes used are manufactured by mono-extrusion, whichis the case for a monolayer pipe, or by coextrusion of the variouslayers, which is the case for a multilayer pipe, according to the usualtechniques for transforming thermoplastics.

To ensure good dimensional stability of a multilayer pipe, it isessential to have excellent adhesion between the various polymer layersforming the tube. Most conventionally, an adhesive layer is interposedbetween two polymer layers, which, by virtue of their composition, donot or do not sufficiently adhere together, to satisfy thespecifications mentioned previously.

More generally, the problem to be solved is that of combininghighl-carbon polyamide materials, which are materials that are veryflexible and very tough (in particular with regard to cold shock, agingin hot air, resistance to zinc chloride), which will generallyconstitute the outer part of the pipe, with barrier materials, i.e.materials that are sparingly permeable to liquids, which will constitutethe inner face of the tube and occasionally come into direct contactwith the liquids, such as gasoline or other fluids mentioned previously.

These barrier materials may be weakly carbonic polyamides, which arepreferably semicrystalline and with a high melting point, but alsonon-polyamide barrier materials such as the copolymer of ethylene andvinyl alcohol (denoted EVOH below), or even functionalized fluoromaterials such as functionalized polyvinylidene fluoride (PVDF), thefunctionalized copolymer of ethylene and tetrafluoroethylene (ETFE), thefunctionalized copolymer of ethylene, tetrafluoroethylene andhexafluoropropylene (EFEP), functionalized polyphenylene sulfide (PPS),or functionalized polybutylene naphthalate (PBN).

DETAILED DESCRIPTION

According to the present invention, the term “polyamide”, also denotedPA, is directed toward:

homopolymers,

copolymers, or copolyamides, based on various amide units, for instancecopolyamide 6/12 with amide units derived from lactam-6 and lactam-12.

The symbol “/” serves to delimit the units of a copolymer.

There is also a category of copolyamides in the broad sense, which,although not preferred, forms part of the context of the invention.These are copolymers bearing PA blocks, especially copolyamidescomprising not only amide units (which will be predominant, hence thefact that they should be considered as copolyamides in the broad sense),but also units of non-amide nature, for example ether units orpolyolefin units. The most commonly known examples are PEBAs orpolyether-block-amide, and the copolyamide-ester-ether,copolyamide-ether and copolyamide ester variants thereof. Among these,mention is made of PEBA-12 in which the polyamide units are the same asthose of PA12, and PEBA-6.12 in which the polyamide units are the sameas those of PA6.12.

Homopolyamides and copolyamides are also distinguished by their numberof carbon atoms per nitrogen atom, given that there are as many nitrogenatoms as there are amide groups (—CO—NH—).

In the case of a homopolyamide of PA-X.Y type, the number of carbonatoms per nitrogen atom is the average of the unit X and of the unit Y.

In the case of copolyamides, the number of carbon atoms per nitrogenatom is calculated according to the same principle. The calculation ismade on the molar pro rata of the various amide units.

A high-carbon polyamide is a polyamide with a high content of carbonatoms (C) relative to the nitrogen atom (N). These are polyamides withat least about 9 carbon atoms per nitrogen atom, for instancepolyamide-9, polyamide-12, polyamide-11, polyamide-10.10 (PA10.10),copolyamide 12/10.T, copolyamide 11/10.T, polyamide-12.T, polyamide-6.12(PA6.12). T represents terephthalic acid.

A weakly carbonic polyamide is a polyamide with a low content of carbonatoms (C) relative to the nitrogen atom (—NH—). These are polyamideswith less than about 9 carbon atoms per nitrogen atom, for instancepolyamide-6, polyamide-6.6, polyamide-4.6, copolyamide-6.T/6.6,copolyamide 6.1/6.6, copolyamide 6.T/6.I/6.6, polyamide 9.T. Irepresents isophthalic diacid.

In the case of a homopolyamide of PA-X.Y type, the number of carbonatoms per nitrogen atom is the average of the unit X and of the unit Y.Thus, PA6.12 is a PA containing 9 carbon atoms per nitrogen atom; inother words it is a C9 PA. PA6.13 is C9.5. PA-12.T is C10, T, i.e.terephthalic acid, being C8.

In the case of copolyamides, the number of carbon atoms per nitrogenatom is calculated according to the same principle. The calculation ismade on the molar pro rata of the various amide units. Thus,coPA-6.T/6.6 60/40 mol% is C6.6: 60%×(6+8)/2+40%×(6+6)/2=6.6. In thecase of a copolyamide bearing units of non-amide type, the calculationis made solely on the amide unit part. Thus, for example, PEBA-12, whichis a block copolymer of 12 amide units and of ether units, the carbonnumber will be 12, as for PA12; for PEBA-6.12, it will be 9, as forPA6.12.

In the case of a copolyamide bearing non-amide units, the calculation ismade solely on the amide unit part. Thus, for example, for PEBA-12 whichis a block copolymer of 12 amide units and of ether units, the number ofcarbon atoms will be 12, as for PA12. For PEBA-6.12, it will be 9, asfor PA6.12.

Thus, high-carbon polyamides such as polyamide PA12 or 11 do not adheresufficiently to an EVOH polymer, to a weakly carbonic polyamide such aspolyamide PA6, or to an alloy of polyamide PA6 and of polyolefin (forinstance an Orgalloy® sold by the company Arkema).

However, it is observed that the structures of pipes currently proposedare not satisfactory for a use intended for biofuel, since therequirements of the motor vehicle constructors' specifications recalledabove cannot all be simultaneously met.

Biofuels are not only derived from petroleum, but comprise a proportionof polar products such as alcohols of plant origin, for instance ethanolor methanol, of at least 3%. This amount may be up to 85%, or even 95%.

In addition, the fuel circulation temperature is tending to rise as aresult of the new engines (more confined, running at a highertemperature).

Binders based on copolyamides are known. Document EP 1 162 061(EMS-Chemie AG) describes, as adhesive or binder, materials based on oneor more copolyamides, these copolyamides consisting of weakly carbonicunits and of high-carbon units. For example, copolyamide 6/12 withrelatively similar proportions of units 6 and of units 12 is used tomake PA12 adhere to PA6, PA12 to EVOH, PA11 to PA6 or PA11 to EVOH.

However, it has been found that such a copolyamide-based adhesivecomposition suffers a large drop in adhesion in hot ethanol or onprolonged contact in polar/apolar mixtures such as hot biofuel(ethanol/gasoline based on apolar hydrocarbons).

All these binders, which are sparingly crystalline, have the drawback oftending to become dissolved and thus of losing their integrity and theirmechanical cohesion in these hot fluids. The adhesion is, as a result,no longer ensured. The problem is all the more critical when the alcoholcontent in the gasoline increases and when the temperature increases.

Adhesive compositions that are no longer based on sparingly crystallineor non-crystalline copolyamides, but based on mixtures of morecrystalline polyamides, by combining, by means of a compatibilizer, ahigh-carbon polyamide such as PA12 with a highly crystalline and/orbarrier and weakly carbonic polyamide such as PA6 (for example in EP 1452 307 and U.S. Pat. No. 6,555,243 from the company EMS-Chemie, in US2004/0 058 111 from the company Saint-Gobain) lead to initial adhesionlevels that are low and insufficient.

Tests were performed using mixtures of crystalline polyamides. Thus, anadhesive composition was prepared comprising 40% of PA6, 40% PA12 and20% of compatibilizer of functionalized EPR type (Exxelor VA1801). Thiscomposition is, admittedly, more resistant to the effect of dissolutionof hot biofuel, but the adhesion remains at a low or moderate level andinsufficient relative to the desired results. The consequences of thispoor adhesion are excessive swelling resulting from the dissociation ofthe layers, and also a permeability to fuels that becomes very highafter immersion or circulation of fuels in the pipe, the leak tightnessno longer being maintained between the layers, and possibly leading toleaks at the joint.

Starting from this observation, it thus becomes necessary to find anadhesive composition that is capable not only of offering sufficientinitial adhesion but is also long-lasting, i.e. sufficient afterprolonged contact in biofuel. This composition must also make itpossible to obtain multilayer pipes that satisfy specifications of motorvehicle constructors, in particular during the use of biofuels.

The present invention is thus directed toward overcoming the drawbacksmentioned above and toward proposing an adhesive composition that isefficient in terms of adhesion to allow its use in multilayer structuresof pipes for transferring fluids, especially fuels, whether they areconventional fuels or biofuels, even for high fluid circulationtemperatures, these circulation temperatures possibly ranging from 40 to150° C. depending on the composition of the fuel: between 60 and 90° C.for gasolines with a very high alcohol content (for example for “E85”,gasoline containing 85% ethanol, which is the reference gasoline inBrazil and Sweden; for example for “E50”, the typical test gasoline inEurope) and between 120 and 150° C. for gasolines with little or noalcohol content (for example lead-free gasoline).

In addition, the adhesive composition according to the invention must beable to be used irrespective of the adjacent layers forming thestructure of the pipes under consideration, and not only with adjacentlayers based on polyamide or EVOH, as in document US 2004/0 265 527.

The present invention is also directed toward providing multilayerstructures using an adhesive composition that overcomes the drawbacksmentioned above.

Finally, the invention relates to a particular copolyamide with a highadhesive power. It has been observed that this power persists even afterprolonged contact in cold or hot fluids, these fluids possibly being ofpolar, apolar and above all mixed nature, such as biofuels.

According to the invention, the adhesive composition predominantlycomprises one or two polyamides consisting of units chosen from:

at least one unit denoted A with a mean number of carbon atoms pernitrogen atom, denoted C_(A), ranging from 4 to 8.5, advantageously from4 to 7;

at least one unit denoted B with a mean number of carbon atoms pernitrogen atom, denoted C_(B), ranging from 7 to 10, advantageously from7.5 to 9.5;

at least one unit denoted C with a mean number of carbon atoms pernitrogen atom, denoted C_(C), ranging from 9 to 18, advantageously from10 to 18; and

optionally at least one unit Z other than an amide unit;

the units A, B and C being present in said polyamide or together in saidpolyamides;

one of the units A, B or C being in a very predominant proportion in thecopolyamide(s) and representing from 80% to 97% by weight relative tothe total weight of the copolyamide,

the mean number of carbon atoms per nitrogen atom of the units A, B andC also corresponding to the following strict inequality:C_(A)<C_(B)<C_(C),

the heat of fusion of the polyamide or the mass-weighted mean of theheats of fusion of the mixture of polyamides in said composition beinggreater than 25 J/g (DSC),

the melting point of the or of each of the polyamides being greater than150° C. (DSC).

The term “one or more units A, B and C” obviously covers mixturescomprising two or more of the units A, B and C as defined above.

It is preferable in the context of the present invention to have 3polyamide units: a unit A, a unit B and a unit C. It neverthelessremains possible to have several units of the same type in thepolyamide(s) of the invention, for instance polyamides of the type A, B,C and also C′; A, B, B′ and C; A, A′, B and C; A, B, B′, C and C′; A,A′, B, B′, C and C′ or alternatively, for example, A, B, C, C′ and C″,in which the units A and A′, for example, correspond to the samedefinition of the unit A.

This adhesive composition has the advantage of being universal, i.e. ofadhering to the polymer layers usually used in the design of the pipesdefined above, namely, compositions based on high-carbon polyamides,such as PA11, PA12, on the one hand, and, on the other hand,compositions based on weakly carbonic polyamides such as PA6, PA6.6,compositions based on EVOH or alloys of weakly carbonic polyamides andof polyolefins.

Furthermore, it has been found that after contact with alcoholicgasolines, at elevated temperature and for a certain time (for example80° C. for 200 hours), such as the gasoline known as E50 comprising bymass 50% of ethanol and 50% of supplemented gasoline (the gasolinepossibly being, for example, of L type supplemented with 5% of water and1% of methanol, according to the Peugeot SA constructor standard B315220, or being, for example, of the “fuel C” type, the latter being amixture of isooctane and of toluene in equal parts), the adhesionremains better than the motor vehicle constructors' recommendationsafter a prolonged duration at high temperature.

Other subjects, aspects and characteristics of the invention will emergeon reading the description that follows.

Moreover, any range of values denoted by the expression “between a andb” represents the range of values extending from more than a to lessthan b (i.e. limits a and b excluded), whereas any range of valuesdenoted by the expression “from a to b” means the range of valuesextending from a to b (i.e. including the strict limits a and b).

Structure of the Polyamide

The nomenclature used to define the polyamides is described in standardISO 1874-1:1992 “Plastics—Polyamide (PA) materials for molding andextrusion—Part 1: Designation”, especially on page 3 (Tables 1 and 2)and is well known to those skilled in the art.

The polyamide(s) according to the invention consists of units chosenfrom:

at least one unit denoted A with a mean number of carbon atoms pernitrogen atom, denoted C_(A), ranging from 4 to 8.5, advantageously from4 to 7;

at least one unit denoted B with a mean number of carbon atoms pernitrogen atom, denoted C_(B), ranging from 7 to 10, advantageously from7.5 to 9.5; and

at least one unit denoted C with a mean number of carbon atoms pernitrogen atom, denoted C_(C), ranging from 9 to 18, advantageously from10 to 18;

optionally at least one unit Z other than an amide unit;

the three units A, B and C being present in said polyamide or togetherin said polyamides;

one of the units A, B or C in the copolyamide(s) being in verypredominant proportion and representing from 80% to 97% by weightrelative to the total weight of the copolyamide,

the mean number of carbon atoms per nitrogen atom of the units A, B andC also corresponding to the following strict inequality:C_(A)<C_(B)<C_(C).

The difference between the mean numbers of carbon atoms per nitrogenatom (C_(B)-C_(A)) and/or (C_(c)-C_(B)) may range from 1 to 4 andpreferably from 2 to 3.

Unit A

The unit A has a ratio between the number of carbon atoms to the numberof nitrogen atoms, denoted C_(A), ranging from 4 to 8.5 andpreferentially from 4 to 7.

The unit A is chosen from units derived from an amino acid, a lactam anda unit corresponding to the formula (Ca diamine).(Cb diacid), with arepresenting the number of carbon atoms in the diamine and brepresenting the number of carbon atoms in the diacid, a and b eachranging from 4 to 13, these units being chosen so as to respect thenumber of carbon atoms to the number of nitrogen atoms, denoted C_(A),ranging from 4 to 8.5. The unit A may denote a mixture of the variousabovementioned units.

When unit A represents a unit derived from a lactam, it may be chosenfrom pyrrolidinone, 2-piperidinone, caprolactam (A=6), enantholactam andcaprylolactam.

When unit A represents a unit derived from a unit corresponding to theformula (Ca diamine).(Cb diacid), the unit (Ca diamine) is chosen fromlinear or branched aliphatic diamines, cycloaliphatic diamines andalkylaromatic diamines.

When the diamine is linear and aliphatic, of formula H₂N—(CH₂)_(a)—NH₂,the monomer (Ca diamine) is preferentially chosen from butanediamine(a=4), pentanediamine (a=5), hexanediamine (a=6), heptanediamine (a=7),octanediamine (a=8), nonanediamine (a=9), decanediamine (a=10),undecanediamine (a=11), dodecanediamine (a=12) and tridecanediamine(a=13).

When the diamine is branched and aliphatic, it may comprise, forexample, one or more methyl or ethyl substituents on the main chain. Forexample, the monomer (Ca diamine) may be chosen advantageously from2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine,1,3-diaminopentane, 2-methyl-1,5-pentanediamine and2-methyl-1,8-octanediamine.

When the monomer (Ca diamine) is cycloaliphatic, it is preferentiallychosen from bis(3,5-dialkyl-4-aminocyclohexyl)methane,bis(3,5-dialkyl-4-aminocyclohexyl)ethane,bis(3,5-dialkyl-4-aminocyclohexyl)propane,bis(3,5-dialkyl-4-aminocyclohexyl)butane,bis(3-methyl-4-aminocyclohexyl)methane (BMACM or MACM),p-bis(aminocyclohexyl)methane (PACM) andisopropylidenedi(cyclohexylamine) (PACP). It may also comprise thefollowing carbon backbones: norbornylmethane, cyclohexylmethane,dicyclohexylpropane, di(methylcyclohexyl), di(methylcyclohexyl)propane.A non-exhaustive list of these cycloaliphatic diamines is given in thepublication “Cycloaliphatic Amines” (Encyclopaedia of ChemicalTechnology, Kirk-Othmer, 4th Edition (1992), pp. 386-405).

When the monomer (Ca diamine) is alkylaromatic, it is preferentiallychosen from 1,3-xylylenediamine and 1,4-xylylenediamine.

When unit A is a unit corresponding to the formula (Ca diamine).(Cbdiacid), the unit (Cb diacid) is chosen from linear or branchedaliphatic diacids, cycloaliphatic diacids and aromatic diacids.

When the monomer (Cb diacid) is linear and aliphatic, it is chosen fromsuccinic acid (b=4), pentanedioic acid (b=5), adipic acid (b=6),heptanedioic acid (b=7), octanedioic acid (b=8), azelaic acid (b=9),sebacic acid (b=10), undecanedioic acid (b=11), dodecanedioic acid(b=12) and brassylic acid (b=13).

When the diacid is cycloaliphatic, it may comprise the following carbonbackbones: norbornylmethane, cyclohexylmethane, dicyclohexylmethane,dicyclohexylpropane, di(methylcyclohexyl) anddi(methylcyclohexyl)propane.

When the diacid is aromatic, it is preferentially chosen fromterephthalic acid (denoted T), isophthalic acid (denoted I) andnaphthalenic diacids.

Preferably, the unit A is chosen from units derived from the followingmonomers: 6, 4.6, 6.6, 6.T, 6.I, 9.T, 9′T, 9′ denoting2-methyl-1,8-octanediamine, i.e. the isomer of diamine-9 or1,9-nonanediamine, 6/6.6, 6.T/6.6, 6.T/6.I/6.6. More particularly, theunit A is chosen from units derived from the following monomers: 6, 4.6and 6.6.

Unit B

Unit B has a ratio between the number of carbon atoms to the number ofnitrogen atoms, denoted C_(B), ranging from 7 to 10 and preferentiallyfrom 7.5 to 9.5.

Unit B is chosen from units derived from an amino acid, a lactam and aunit corresponding to the formula (Cc diamine).(Cd diacid), with crepresenting the number of carbon atoms in the diamine and drepresenting the number of carbon atoms in the diacid, c and d eachranging from 4 to 16, these units being chosen so as to respect thenumber of carbon atoms to the number of nitrogen atoms, denoted CB,ranging from 7 to 10. Unit B may denote a mixture of the variousabovementioned units.

When unit B represents a unit derived from an amino acid, it may bechosen from 9-aminononanoic acid (B=9) or 10-aminodecanoic acid (B=10).

When unit B represents a unit derived from a lactam, it may be chosenfrom enantholactam, caprylolactam, pelargolactam and decanolactam.

When unit B represents a unit derived from a unit corresponding to theformula (Cc diamine).(Cd diacid), the unit (Cc diamine) is chosen fromlinear or branched aliphatic diamines, cycloaliphatic diamines andalkylaromatic diamines.

When the diamine is linear and aliphatic, of formula H₂N—(CH₂)_(c)—NH₂,the monomer (Cc diamine) is preferentially chosen from butanediamine(c=4), pentanediamine (c=5), hexanediamine (c=6), heptanediamine (c=7),octanediamine (c=8), nonanediamine (c=9), decanediamine (c=10),undecanediamine (c=11), dodecanediamine (c=12), tridecanediamine (c=13),tetradecanediamine (c=14) and hexadecanediamine (c=16).

When the diamine is branched and aliphatic, it may comprise one or moremethyl or ethyl substituents on the main chain. For example, the monomer(Cc diamine) may be chosen advantageously from2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine,1,3-diaminopentane, 2-methyl-1,5-pentanediamine and2-methyl-1,8-octanediamine.

When the monomer (Cc diamine) is cycloaliphatic, it is preferentiallychosen from bis(3,5-dialkyl-4-aminocyclohexyl)methane,bis(3,5-dialkyl-4-aminocyclohexyl) ethane,bis(3,5-dialkyl-4-aminocyclohexyl)propane,bis(3,5-dialkyl-4-aminocyclohexyl)butane,bis(3-methyl-4-aminocyclohexyl)methane (BMACM or MACM),p-bis(aminocyclohexyl)methane (PACM) andisopropylidenedi(cyclohexylamine) (PACP). It may also comprise thefollowing carbon backbones: norbornyl methane, cyclohexylmethane,dicyclohexylpropane, di(methylcyclohexyl), di(methylcyclohexyl)propane.A non-exhaustive list of these cycloaliphatic diamines is given in thepublication “Cycloaliphatic Amines” (Encyclopaedia of ChemicalTechnology, Kirk-Othmer, 4th Edition (1992), pp. 386-405).

When the monomer (Cc diamine) is alkylaromatic, it is preferentiallychosen from 1,3-xylylene diamine and 1,4-xylylene diamine.

When unit B represents a unit derived from a unit corresponding to theformula (Cc diamine).(Cd diacid), the unit (Cd diacid) is chosen fromlinear or branched aliphatic diacids, cycloaliphatic diacids andaromatic diacids.

When the monomer (Cd diacid) is linear and aliphatic, it ispreferentially chosen from succinic acid (d=4), pentanedioic acid (d=5),adipic acid (d=6), heptanedioic acid (d=7), octanedioic acid (d=8),azelaic acid (d=9), sebacic acid (d=10), undecanedioic acid (d=11),dodecanedioic acid (d=12), brassylic acid (d=13), tetradecanedioic acid(d=14) and hexadecanedioic acid (d=16).

When the diacid is cycloaliphatic, it may comprise the following carbonbackbones: norbornyl methane, cyclohexylmethane, dicyclohexylmethane,dicyclohexylpropane, di(methylcyclohexyl), di(methylcyclohexyl)propane.

When the diacid is aromatic, it is preferentially chosen fromterephthalic acid (denoted T), isophthalic acid (denoted I) andnaphthalenic diacids.

Preferably, unit B represents a unit chosen from the following monomers:6.10, 6.12, 9.T and 9′.T, 6.14, 6.10/6.12. More particularly, unit Bdenotes the monomer 6.10 or 6.12.

Unit C

Unit C has a ratio between the number of carbon atoms to the number ofnitrogen atoms, denoted C_(C), ranging from 9 to 18 and preferentiallyfrom 10 to 18.

Unit C is chosen from units derived from an amino acid, a lactam and aunit corresponding to the formula (Ce diamine).(Cf diacid), with erepresenting the number of carbon atoms in the diamine and frepresenting the number of carbon atoms in the diacid, e and f eachranging from 4 to 32, these units being chosen so as to respect thenumber of carbon atoms to the number of nitrogen atoms, denoted C_(B),ranging from 9 to 18. Unit C may denote a mixture of the variousabovementioned units.

When unit C represents a unit derived from an amino acid, it may bechosen from 9-aminononanoic acid (C=9), 10-aminodecanoic acid (C=10),10-aminoundecanoic acid (denoted 11), 12-aminododecanoic acid (C=12) and11-aminoundecanoic acid (C=11), and also derivatives thereof, especiallyN-heptyl-11-aminoundecanoic acid.

When unit C represents a unit derived from a lactam, it may be chosenfrom pelargolactam, decanolactam, undecanolactam, and lauryllactam(C=12).

When unit C represents a unit derived from a unit corresponding to theformula (Ce diamine).(Cf diacid), the unit (Ce diamine) is chosen fromlinear or branched aliphatic diamines, cycloaliphatic diamines andalkylaromatic diamines.

When the diamine is linear and aliphatic, of formula H₂N—(CH₂)e-NH₂, themonomer (Ce diamine) is preferentially chosen from butanediamine (e=4),pentanediamine (e=5), hexanediamine (e=6), heptanediamine (e=7),octanediamine (e=8), nonanediamine (e=9), decanediamine (e=10),undecanediamine (e=11), dodecanediamine (e=12), tridecanediamine (e=13),tetradecanediamine (e=14), hexadecanediamine (e=16), octadecanediamine(e=18), octadecenediamine (e=18), eicosanediamine (e=20),docosanediamine (e=22) and the diamines obtained from fatty acids.

When the diamine is branched and aliphatic, it may comprise one or moremethyl or ethyl substituents on the main chain. For example, the monomer(Ce diamine) may be chosen advantageously from2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine,1,3-diaminopentane, 2-methyl-1,5-pentanediamine and2-methyl-1,8-octanediamine.

When the monomer (Ce diamine) is cycloaliphatic, it is preferentiallychosen from bis(3,5-dialkyl-4-aminocyclohexyl)methane,bis(3,5-dialkyl-4-aminocyclohexyl)ethane,bis(3,5-dialkyl-4-aminocyclohexyl)propane,bis(3,5-dialkyl-4-aminocyclohexyl)butane,bis(3-methyl-4-aminocyclohexyl)methane (BMACM or MACM),p-bis(aminocyclohexyl)methane (PACM) andisopropylidenedi(cyclohexylamine) (PACP). It may also comprise thefollowing carbon backbones: norbornyl methane, cyclohexylmethane,dicyclohexylpropane, di(methylcyclohexyl), di(methylcyclohexyl)propane.A non-exhaustive list of these cycloaliphatic diamines is given in thepublication “Cycloaliphatic Amines” (Encyclopaedia of ChemicalTechnology, Kirk-Othmer, 4th Edition (1992), pp. 386-405).

When the monomer (Ce diamine) is alkylaromatic, it is preferentiallychosen from 1,3-xylylene diamine and 1,4-xylylene diamine.

When unit C is a unit corresponding to the formula (Ce diamine).(Cfdiacid), the unit (Cf diacid) is chosen from linear or branchedaliphatic diacids, cycloaliphatic diacids and aromatic diacids.

When the monomer (Cf diacid) is linear and aliphatic, it ispreferentially chosen from succinic acid (f=4), pentanedioic acid (f=5),adipic acid (f=6), heptanedioic acid (f=7), octanedioic acid (f=8),azelaic acid (f=9), sebacic acid (f=10), undecanedioic acid (f=11),dodecanedioic acid (f=12), brassylic acid (f=13), tetradecanedioic acid(f=14), hexadecanedioic acid (f=16), octadecanedioic acid (f=18),octadecenedioic acid (f=18), eicosanedioic acid (f=20), docosanedioicacid (f=22) and fatty acid dimers containing 36 carbons.

The fatty acid dimers mentioned above are dimerized fatty acids obtainedby oligomerization or polymerization of unsaturated monobasic fattyacids bearing a long hydrocarbon-based chain (such as linoleic acid andoleic acid), as described especially in document EP 0 471 566.

When the diacid is cycloaliphatic, it may comprise the following carbonbackbones: norbornyl methane, cyclohexylmethane, dicyclohexylmethane,dicyclohexylpropane, di(methylcyclohexyl), di(methylcyclohexyl)propane.

When the diacid is aromatic, it is preferentially chosen fromterephthalic acid (denoted T), isophthalic acid (denoted I) andnaphthalenic diacids.

Unit C represents a unit chosen from the derivatives of the followingmonomers: 12, 11, 10.10, 10.12, 6.18, 10.T, 12.T, 12/10.T, 12.12,10.10/10.12 and 10.10/10.T. More particularly, unit C denotes themonomer 12, 11, 10.10 or 10.12.

The units used for the polyamide(s) of the composition according to theinvention are preferably aliphatic polyamides.

Heat of Fusion

The heat of fusion of the polyamide or the mass-weighted mean of theheats of fusion of the mixture of polyamides according to the inventionin said composition is greater than 25 J/g (DSC), measured by DSC inaccordance with standard ISO 11357.

Thus, the polyamide(s) according to the invention are subjected to afirst heating from 20° C./min up to a temperature of 340° C., followedby cooling at 20° C./min to a temperature of 20° C., and then a secondheating of 20° C./min up to a temperature of 340° C., the heat of fusionbeing measured during this second heating.

Preferably, the heat of fusion ranges from 30 J/g to 60 J/g.

Melting Point

The melting point of the or of each of the polyamides is greater than150° C., measured by DSC (Differential Scanning Calorimetry) inaccordance with standard ISO 11357.

Preferably, the melting point ranges from 155 to 300° C.

Preferably, the melting point of the homopolyamide consisting of unit Ais greater than or equal to 210° C.

Preferably, the melting point of the homopolyamide consisting of unit Cis less than 200° C.

Contents

Preferably, the predominant unit A, B or C represents from 85% to 95% byweight relative to the total weight of amide units in the polymer(whether the polyamide consists solely of amide units or not (in thecase of A/B/C/Z, Z being a PEBA, for example)).

It is recalled that the term “polyamide” includes homopolyamides andcopolyamides, and that the copolyamides include terpolyamides.

Unit Z

The polyamide(s) according to the invention may comprise at least oneunit Z other than an amide unit. Preferably, this unit is chosen fromether, ester and α-olefin units. In other words, the polyamide(s)according to the invention may comprise a polyether (PE), polyester orpolyolefin block.

Ether Units

The PE block comprises alkylene oxide units. These units may be ethyleneoxide, propylene oxide or tetrahydrofuran units (which leads topolytetramethylene glycol sequences). Advantageously, said PE blockincluded in the copolymer according to the invention is chosen frompolyethylene glycol (PEG), i.e. consists of ethylene oxide units,polypropylene glycol (PPG), i.e. consists of propylene oxide units,polytetramethylene glycol (PTMG), i.e. consists of tetramethylene glycolunits, and copolymers thereof. The copolymer according to the inventionmay comprise several types of polyethers, the copolyethers possiblybeing in block or random form.

Use may also be made of blocks obtained by oxyethylation of bisphenols,for instance bisphenol A. These latter products are described in patentEP 613 919.

The polyether blocks may also consist of ethoxylated primary amines.Examples of ethoxylated primary amines that may be mentioned include theproducts of formula:

in which m and n are between 1 and 20 and x is between 8 and 18. Theseproducts are commercially available under the brand name Noramox® fromthe company CECA and under the brand name Genamin® from the companyClariant.

The polyether (PE) blocks may comprise polyoxyalkylene blocks with NH₂chain ends, such blocks possibly being obtained by cyanoacetylation ofaliphatic α,ω-dihydroxylated polyoxyalkylene blocks known aspolyetherdiols. More particularly, use may be made of the Jeffamineproducts (for example Jeffamine® D400, D2000, ED 2003, XTJ 542,commercial products from the company Huntsman, also described in patentsJP 2004/346 274, JP 2004/352 794 and EP 1 482 011).

Ester Units

The polyester (PES) block that may be used according to the invention isa polyester obtained by polycondensation between a dicarboxylic acid anda diol. The appropriate carboxylic acids include those mentioned aboveused for forming the polyamide blocks with the exception of aromaticacids, such as terephthalic acid and isophthalic acid. The appropriatediols comprise linear aliphatic diols such as ethylene glycol,1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexylene glycol, brancheddiols such as neopentyl glycol, 3-methylpentane glycol, 1,2-propyleneglycol, and cyclic diols such as 1,4-bis(hydroxymethyl)cyclohexane and1,4-cyclohexanedimethanol. An example of a polyester used is thepolyadipate family.

The term “polyesters” also means poly(caprolactone) and PESs based onfatty acid dimers, in particular the products of the Priplast® rangefrom the company Uniqema.

A PES block of alternating, random or block “copolyester” type,containing a sequence of at least two types of PES mentioned above, mayalso be envisaged.

Polyolefin Unit

The polyolefin (PO) block that may be used according to the invention isa polymer comprising as monomer an α-olefin, i.e. homopolymers of anolefin or copolymers of at least one α-olefin and of at least one othercopolymerizable monomer, the α-olefin advantageously containing from 2to 30 carbon atoms.

Examples of α-olefins that may be mentioned include ethylene, propylene,1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene,3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene,1-hexadecene, 1-octadecene, 1-eicocene, 1-dococene, 1-tetracocene,1-hexacocene, 1-octacocene, and 1-triacontene. These α-olefins may beused alone or as a mixture of two or more than two.

Examples that may be mentioned include:

ethylene homopolymers and copolymers, in particular low-densitypolyethylene (LDPE), high-density polyethylene (HDPE), linearlow-density polyethylene (LLDPE), very low-density polyethylene (VLDPE),and polyethylene obtained by metallocene catalysis,

propylene homopolymers and copolymers,

essentially amorphous or attactic poly-α-olefins (APAO),

ethylene/α-olefin copolymers such as ethylene/propylene, EPR(ethylene-propylene-rubber) and EPDM (ethylene-propylene-diene)elastomers, and mixtures of polyethylene with an EPR or an EPDM,

styrene/ethylene-butene/styrene (SEBS), styrene/butadiene/styrene (SBS),styrene/isoprene/styrene (SIS) and styrene/ethylene-propylene/styrene(SEPS) block copolymers,

copolymers of ethylene with at least one product chosen from salts oresters of unsaturated carboxylic acids, for instance alkyl(meth)acrylates, the alkyl possibly containing up to 24 carbon atoms,vinyl esters of saturated carboxylic acids, for instance vinyl acetateor propionate, and dienes, for instance 1,4-hexadiene or polybutadiene.

According to one advantageous embodiment of the invention, said at leastone polyolefin block comprises a polyisobutylene and/or polybutadiene,which is optionally hydrogenated.

Preferably, the predominant unit Z represents from 0% to less than 50%by weight relative to the total weight of the polyamide.

Preferably, the polyamide(s) according to the invention comprise onlyamide units.

Preferably, the polyamide or the two polyamides according to theinvention denote(s) a terpolyamide, a homopolyamide combined with acopolyamide or two copolyamides.

First Embodiment

For the purposes of the present invention, the term “terpolyamide” meansa copolyamide consisting of units A, B and C.

According to a first embodiment of the invention, the polyamide includedin the adhesive composition of the invention is a terpolyamideconsisting of the three abovementioned units A, B and C.

As outlined above, the terpolyamide according to the invention maycomprise more than three different units, but these units mustnecessarily be units A, B and C as described above. The terpolyamide maybe, for example, of the following structure: A/B/C, A/A′/B/B′/C/C′ orA/A′/A″/B/C.

Preferably, the terpolyamide according to the invention comprises onlyone unit A, only one unit B and only one unit C.

Preferably, unit B is the predominant unit, and is present in aproportion representing from 85% to 95% by weight relative to the totalweight of the terpolyamide.

Preferably, the amide unit A is chosen from units derived from thefollowing monomers: 6, 4.6, 6.6, 6.T, 9.T and 9′.T, 9′ denoting2-methyl-1,8-octanediamine;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, 9.T and 9′.T, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 6.18, 10.T, 12.T, 12/10.T, 12.12 and10.10/10.T.

More particularly, the amide unit A is chosen from units derived fromthe following monomers: 6, 4.6 and 6.6;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 12.12 and 6.18.

The preferred terpolyamide is chosen from PA 6/6.10/12, PA 6/6.12/12 andPA 6.6/6.10/12.

Second Embodiment

According to a second embodiment of the invention, the polyamidesincluded in the adhesive composition of the invention are a mixture oftwo different copolyamides each consisting of two units chosen from theabovementioned units A, B and C.

Thus, this embodiment covers the following combinations of copolyamides:PA A/B+PA A/C; PA A/B+PA B/C and PA A/C+PA B/C or alternatively PAA/B+PA A′/C; PA A/B+PA B′/C and PA A/C+PA B/C′.

Preferably, the preferred combination is that in which unit B is presentin the two copolyamides, namely the combination PA A/B+PA B/C.

Preferably, in this particular combination, unit A is the predominantunit in the copolyamide A/B and unit C is the predominant unit in thecopolyamide B/C.

Preferably, the amide unit A is chosen from units derived from thefollowing monomers: 6, 4.6, 6.6, 6.T, 9.T and 9′.T;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, 9.T and 9′.T, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 6.18, 10.T, 12.T, 12/10.T, 12.12 and10.10/10.T.

More particularly, the amide unit A is chosen from units derived fromthe following monomers: 6, 4.6 and 6.6;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 12.12 and 6.18.

Preferably, the preferred combinations are PA6.6/6.10 and PA6.12/12;PA6/6.12 and PA6.12/12; and finally PA6/6.10 and PA6.10/12.

Third Embodiment

According to a third embodiment of the invention, the polyamidesincluded in the adhesive composition of the invention are a mixture of acopolyamide consisting of two units chosen from the abovementioned unitsA, B and C and of a homopolyamide consisting of the unit that is absentfrom the copolyamide.

Thus, this embodiment covers the following combinations of copolyamides:PA A/B+PA C; PA A/C+PA B and PA B/C+PA A.

In the case of the combination PA A/B+PA C, unit A is preferentially thepredominant unit in the copolyamide A/B.

In the case of the combination PA B/C+PA A, unit C is preferentially thepredominant unit in the copolyamide B/C.

More particularly, the preferred combination is PA B/C+PA A, i.e. ahomopolyamide predominantly comprising units A, and more particularlyonly one unit A, combined with a copolyamide B/C, unit B being thepredominant unit in the copolyamide B/C.

Preferably, the amide unit A is chosen from units derived from thefollowing monomers: 6, 4.6, 6.6, 6.T, 9.T and 9′.T;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, 9.T and 9′.T, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 6.18, 10.T, 12.T, 12/10.T, 12.12 and10.10/10.T.

More particularly, the amide unit A is chosen from units derived fromthe following monomers: 6, 4.6 and 6.6;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 12.12 and 6.18.

More particularly, the preferred combinations are PA6 and PA6.12/12 andPA6 and PA6.10/12.

It would not constitute a departure from the context of the presentinvention if the homopolyamide were replaced with a copolyamidecomprising in very minor amount a unit of the same type as thepredominant unit, for instance a copolyamide PA A/A′, PAB/B′ or PA C/C′.

The homopolyamides and copolyamides used in the embodiments describedabove may comprise a unit other than an amide unit. Thus, it is possibleto envisage

a terpolyamide having the following structure: A/B/C/Z, Z denoting aunit other than an amide unit,

a mixture of two different copolyamides each consisting of two unitschosen from the abovementioned units A, B and C and of a unit Z otherthan an amide unit.

Thus, this embodiment covers the following combinations of copolyamides:PA A/B/Z+PA A/C; PA A/B+PA A/C/Z; PA A/B/Z+PA B/C; PA A/B+PA B/C/Z; PAA/C/Z+PA B/C and PA A/C+PA B/C/Z;

a mixture of a copolyamide consisting of two units chosen from theabovementioned units A, B and C, of a homopolyamide consisting of theunit that is absent from the copolyamide and of a unit Z other than anamide unit.

Thus, this embodiment covers the following combinations of copolyamides:PA A/B/Z+PA C; PA A/C/Z+PA B; PA B/C/Z+PA A; PA A/B +PA C/Z; PA A/C+PAB/Z and PA B/C+PA A/Z.

Preferably, the polyamide(s) according to the invention comprise onlyamide units.

Nature of the Possible Additives

Thus, the composition may comprise up to 30% by weight, relative to thetotal weight of the composition, of an impact modifier consisting of anon-rigid polymer with a flexural modulus of less than 100 MPa measuredaccording to standard ISO 178.

This non-rigid polymer is preferably as supple as possible and has thelowest possible glass transition temperature Tg, i.e. less than 0° C.This impact modifier is, if need be, chemically functionalized so as tobe able to react with the polyamides A, B and C and to form an alloythat is compatible therewith.

According to the invention, the impact modifier preferably consists ofone or more polyolefins, some or all thereof bearing a function chosenfrom carboxylic acid, carboxylic anhydride and epoxide functions or anyother function that is capable of reacting chemically with thepolyamides, typically with its amine chain ends (which is the case forcarboxylic acid and carboxylic anhydride) or its acid chain ends (whichis the case for epoxide, in particular glycidyl methacrylate).

For example, the polyolefin is chosen from:

a copolymer of ethylene and propylene of elastomeric nature (EPR),

an ethylene-propylene-diene copolymer of elastomeric nature (EPDM) and

an ethylene/alkyl (meth)acrylate copolymer.

Among the impact modifiers, mention is made of anhydride-grafted EPRsuch as Exxelor VA1803 from Exxon, or the copolymer of polyethylene,ethyl acrylate and maleic anhydride (coPE/EA/MAH) such as Lotader 4700from the company Arkema.

Polyolefin

The adhesive composition may also comprise up to 45% by weight, relativeto the total weight of the composition, of a crystalline polymer with aflexural modulus, measured according to standard ISO 178, of greaterthan 300 MPa and advantageously greater than 800 MPa.

This crystalline polymer is preferably a semicrystalline rigidpolyolefin, or a mixture of semicrystalline rigid polyolefins, bearing,totally or partially, a function chosen from carboxylic acid, carboxylicanhydride and epoxide functions.

Preferably, the polyolefin, or the mixture of polyolefins, is chosenfrom high-density polyethylenes and homopolymeric or sparinglycopolymerized polypropylenes.

When it is a polyolefin with a high degree of crystallinity, it may be,for example, a high-density polyethylene, denoted HDPE, or afunctionalized high-density polyethylene, denoted HDPE, functionalizedwith a reactive group that can react with one of the chain ends (orother reactive functions) of the polyamide; this function is typicallyan anhydride function, or a high-density polypropylene (PP), typically alinear rigid PP, of homopolymeric or very slightly copolymerized type.

The composition may also comprise up to 20% by weight, relative to thetotal weight of the composition, of a plasticizer.

Other Additives

The composition may also comprise up to 45% by weight, relative to thetotal weight of the composition, of an additive chosen from antistaticfillers, nucleating agents, lubricants, colorants, pigments, opticalbrighteners, antioxidants and stabilizers.

The usual stabilizers used with polymers are phenols, phosphites, UVabsorbers, stabilizers of the HALS type (hindered-amine lightstabilizer), metal iodides, etc. Mention may be made of lrganox 1010,245, 1098, lrgafos 168, Tinuvin 312, Iodide P201 from the company Ciba.

Peel Strength

The composition according to the invention preferably has a peelstrength of greater than 60 N/cm. The adhesion test under considerationis performed on a pipe 8 mm in diameter and 1 mm thick. One of thelayers is peeled off by subjecting it to traction at an angle of 90° andat a speed of 50 mm/min.

Thus, advantageously, the adhesive composition according to theinvention has an adhesion force of at least 60 N/cm, when it is betweena layer of PA 12 and a layer of PA6 or of EVOH, and of at least 10 N/cm,preferably at least 20 N/cm, after a residence time of 72 hours at 80°C. in a mixture of E50 type biofuel (corresponding to a mixturecomprising by mass 50% of ethanol and 50% of supplemented gasoline (thegasoline possibly being, for example, of L type supplemented with 5% ofwater and 1% of methanol, according to the Peugeot SA constructorstandard B31 5220, or being, for example, of the “Fuel C” type, thelatter being a mixture of isooctane and of toluene in equal parts); theadhesion remains greater than the motor vehicle constructors'recommendations.

Thus, this adhesion test under difficult conditions (immersion in abiofuel for a long time and at high temperature) is one of thecharacteristics required for resolving the posed technical problem.

Furthermore, in order to ensure good properties (flexibility, burststrength, tear strength, transparency, rheology, transformability intopipe or a film, nucleation, crystallization, morphology, alloying,compatibilization, homogeneity, consistency, adhesion) and, inparticular, good properties of resistance to impacts and to impactsafter aging (especially high-temperature oxidative aging), it ispossible to add to the adhesive composition an impact-modifyingcompatibilizer of elastomeric and preferentially polar nature.

Use

The invention relates to the use of the adhesive composition as definedabove for making structures for transferring and/or storing fluids, inparticular a fluid chosen from an oil, a brake liquid, a cooling liquid,a urea solution, a hydrocarbon, a diesel, a gasoline, in particular agasoline comprising a high proportion of alcohols such as ethanol,compressed air.

The invention also relates to the use of the composition as definedabove as an adhesive layer in a multilayer structure.

A subject of the invention is also a monolayer structure predominantlycomprising at least one composition as defined above.

Structure

The symbol “//” serves to delimit the layers of a multilayer structure.

Finally, the invention relates to a multilayer structure, i.e. astructure comprising at least two layers, one of the two layers, knownas the adhesive layer or binder, denoted (I), being formed from anadhesive composition as defined above.

According to a first embodiment of the invention, the second layer is alayer known as the barrier layer (II).

According to a first advantageous variant of the invention, the barrierlayer (II) may be formed by a composition comprising at least onepolymer that is a barrier to biofuels, preferably chosen from EVOH,weakly carbonic polyamide, i.e. in which the ratio of the number ofcarbon atoms to the number of nitrogen atoms ranges from 4 to 7, and amixture thereof.

Thus, in a two-layer structure or a multilayer structure, the secondlayer may comprise a barrier material, which may be chosen from:

either a composition comprising a copolymer of ethylene and vinylalcohol (EVOH),

or weakly-carbonic polyamides, for example amorphous weakly carbonicpolyamides of high Tg (80-200° C.).

According to a second advantageous variant of the invention, the barrierlayer (II) may be formed by a composition comprising a weakly carbonicpolyamide, as explained above, and a crystalline polymer with a flexuralmodulus, measured according to standard ISO 178, of greater than 300MPa, advantageously greater than 800 MPa.

Preferably, the crystalline polymer is a rigid semicrystallinepolyolefin, or mixture of polyolefins, with a flexural modulus, measuredaccording to standard ISO 178, of greater than 300 MPa, the rigidpolyolefin bearing, totally or partially, a function chosen fromcarboxylic acid, carboxylic anhydride and epoxide functions.

For example, the following composition may be used: an alloy composed ofa matrix made of polyamide 6 of Mn 18 000 (for example Ultramid B27 fromthe company BASF), and 30% of HDPE (high-density polyethylene) with adensity of 0.96 and a melt flow index of 0.3 (at 190° C. under 2.16 kg),7% of HDPE functionalized by grafting 1% of maleic anhydride, with amelt flow index of 1 (at 190° C. under 2.16 kg), 1.2% of organicstabilizers (consisting of 0.8% of phenol Lowinox 44B25 from the companyGreat Lakes), 0.2% of phosphite Irgafos 168 from the company Ciba, 0.2%of anti-UV agent (Tinuvin 312 from the company Ciba), the whole making100%.

Other compositions are envisagable for making the barrier layer (II).

According to a third advantageous variant of the invention,polymer-based compositions may also be envisaged, these polymerspreferably being functionalized with anhydride or with another functionthat is reactive with the amine or acid chain ends. Mention may be madein a nonlimiting manner of flouro polymers, such as polyvinylidenefluoride (PVDF), the copolymer of ethylene and of tetrafluoroethylene(ETFE), the copolymer of ethylene, of tetrafluoroethylene and ofhexafluoropropylene (EFEP), or nonfluoro polymers such as polyphenylenesulfide (PPS), polybutylene naphthalate (PBN). These fluoro polymers(PVDF, ETFE, EFEP) and nonfluoro polymers (PPS, PBN) will preferentiallybe functionalized.

The adhesive layer (I) and barrier layer (II) of the two-layer ormultilayer structures that have just been described show excellentadhesion to each other, which adhesion is not deteriorated even byprolonged residence in a gasoline comprising alcohols (biofuel).

In addition, this barrier layer (II), in its three variants describedabove, is very sparingly permeable to liquids, and especially to fuels.Consequently, this layer (II) is generally at the end of the structure,in contact with the liquids or subjacent to a layer that is in contactwith the liquids.

According to this particular embodiment formed by the two-layerstructure (I)/(II), the adhesive layer (I) may have long-lastingproperties. It may then constitute the outer layer or support for thetwo-layer structure.

According to a second embodiment of the invention, the structurecomprises at least a third layer, known as the “long-lasting layer”(III), the adhesive layer (I) according to the invention being arrangedbetween said long-lasting layer (III) and the barrier layer (II) andadhering to the respective zone of contact thereof.

Thus, the multilayer structure may consist of three layers, in thefollowing successive order:

a long-lasting layer (III) comprising the long-lasting materials asdefined below,

an adhesive layer (I) comprising the adhesive composition according tothe invention, and

a barrier layer (II) comprising the barrier materials as defined above.

The long-lasting layer (III) may be formed from a composition comprisinghigh-carbon polyamide, i.e. in which the ratio of the number of carbonatoms to the number of nitrogen atoms ranges from 10 to 18 as explainedabove. Specifically, the high-carbon polyamide offers noteworthyproperties such as noteworthy longevity, especially noteworthyresistance to aging and to degradation in corrosive, humid and oxidativemedia, for instance resistance in hot air or in hot chemical products.The high-carbon polyamide has great resistance to stress cracking, tozinc chloride and to chemical products in general. The high-carbonpolyamide also has good dimensional stability in media of variablehumidity. It is also resistant to impacts.

Preferably, the high-carbon polyamide is chosen from PA11, PA12,PA10.10, PA10.12, PA12/10.T, PA10.10/10.T and mixtures thereof.

The long-lasting layer (III) comprising the high-carbon polyamidedefined above may also be chosen to constitute the support or outerlayer of the multilayer structure.

On the basis of these three types of layers, the long-lasting layer(III), the adhesive layer (I) and the barrier layer (II), it is possibleto produce numerous structures that may comprise up to 6 layers, usingadditional barrier, adhesive or long-lasting layers.

It is possible, according to a third embodiment of the invention, to usetwo layers of barrier materials, for instance a layer of a copolymer ofethylene and vinyl alcohol (EVOH) and a layer of a weakly carbonicpolyamide combined with a particular polyolefin, the combination ofthese two barrier layers having synergistic properties.

According to a fourth embodiment of the invention, the structurecomprises, in the following order:

a third layer, known as the long-lasting layer (III),

the adhesive layer (I) comprising the adhesive composition according tothe invention,

a second layer, known as the barrier layer (II),

a fourth layer (IV),

the layers adhering together via the respective zone of contact thereof.

Preferably, the structure may comprise the following successive layers:

a third long-lasting layer (III) formed from a composition comprisingpolyamide C,

the adhesive layer (I) comprising the adhesive composition according tothe invention,

a second barrier layer (II) formed from a composition comprising EVOH,and

a fourth layer formed from a composition comprising weakly carbonicpolyamide.

The composition comprising the weakly carbonic polyamide of the barrierlayer (II) and/or of the fourth layer (IV) may also comprise at leastone rigid semicrystalline polyolefin, or mixture of polyolefins, with aflexural modulus, measured according to standard ISO 178, of greaterthan 300 MPa.

Structures of this type have the advantage of having a particularly highbarrier effect toward biofuel with minor contents of ethanol.

It is also possible, according to a fifth embodiment of the invention,to reinforce the outer part of the structure by inserting, between theadhesive layer (I) and the first long-lasting layer (III), a secondlong-lasting layer as defined above, for example a long-lasting layerwith improved impact strength, said second long-lasting layer adheringto the adjacent layers on the respective zone of contact thereof.

Moreover, it turns out that the adhesive layer (I) may also have theproperties of a barrier material. Consequently, it is possible,according to a sixth embodiment of the invention, to position it at anend of the structure and in contact with the liquids, and to do so

in a two-layer structure in combination with a long-lasting layer,

in a three-layer structure, or

in a four-layer structure.

According to a seventh embodiment of the invention, it is also possibleto envisage the following structure comprising the following 5successive layers:

long-lasting layer (III),

adhesive layer (I),

barrier layer (II),

adhesive layer (I),

barrier layer (II),

the layers adhering together via the respective zone of contact thereof.

According to an eighth embodiment of the invention, the long-lastinglayer (III) may also be at each of the ends of the structure. Thesestructures have better resistance to ZnCl₂ and to peroxide media (rancidgasoline or gas oil). These structures also have the advantage of havingbetter impact strength performance. For example, this structure may be athree-layer structure, thus leading to symmetrical structures.

According to a ninth embodiment of the invention, it is possible to makesymmetrical structures comprising, for example, the following successionof layers:

a long-lasting layer (III),

an adhesive layer (I) according to the invention,

a barrier layer (II),

a second adhesive layer (I),

a second long-lasting layer (III),

the layers adhering together via the respective zone of contact thereof.

Preferably, the structure comprises the following five successivelayers:

a long-lasting layer (III) formed from a composition comprisinghigh-carbon polyamide,

the adhesive layer denoted (I),

a barrier layer (II) formed from a composition comprising EVOH,

another adhesive layer (I), and

a long-lasting layer (III) formed from a composition comprisinghigh-carbon polyamide,

the layers adhering together via the respective zone of contact thereof.

The thickness of the adhesive layer (I) advantageously ranges from 25 to1000 μm and preferably from 25 to 150 μm, when it serves as binder.

The structures described above may be in the form of a pipe, acontainer, a film or a plate.

When these structures are in the form of a pipe, they may be used fortransporting and storing fluids, especially present in vehicles,especially for transporting polar and/or apolar liquids, for instance anoil, a brake liquid, a urea solution, a glycol-based cooling liquid,fuels, such as polar or apolar fuels, diesel, biodiesel, i.e. apolarhydrocarbons and esters, in particular gasoline, most particularlybiofuel, i.e. apolar hydrocarbons and alcohol such as ethanol andmethanol, and compressed air.

Such structures are particularly advantageous for transporting gasoline,biofuel, biodiesel and cooling liquid, conventionally based on glycol,and a mixture of urea and water.

The invention relates finally to a polyamide consisting of the followingunits:

a unit denoted A with a mean number of carbon atoms per nitrogen atom,denoted C_(A), ranging from 4 to 8.5, advantageously from 4 to 7;

a unit denoted B with a mean number of carbon atoms per nitrogen atom,denoted C_(B), ranging from 7 to 10, advantageously from 7.5 to 9.5; and

a unit denoted C with a mean number of carbon atoms per nitrogen atom,denoted C_(C), ranging from 9 to 18, advantageously from 10 to 18;

optionally at least one unit Z other than an amide unit;

one of the units A, B or C being in very predominant proportion in thepolyamide and representing from 80% to 97% by weight relative to thetotal weight of the polyamide,

the mean number of carbon atoms per nitrogen atom of the units A, B andC also corresponding to the following strict inequality:C_(A)<C_(B)<C_(C),

the heat of fusion of the polyamide being greater than 25 J/g (DSC),

the heat of fusion of the polyamide being greater than 150° C. (DSC).

The units A, B and C are as defined above.

Preferably, the polyamide according to the invention consists of asingle unit A, of a single unit B and of a single unit C.

Preferably, unit B is the very predominant unit in the polyamideaccording to the invention.

The examples that follow serve to illustrate the invention without,however, being limiting in nature.

EXAMPLES

1/When the Composition According to the Invention Comprises aTerpolyamide Consisting of Units A, B and C

1.1 Preparation of the Compositions

The compositions according to the invention given in Table 1 wereprepared from the following components. The amounts of products areexpressed as weight percentages relative to the total weight of thecomposition.

PA 6/6.12/12 (6%/88%/6%) denotes a copolyamide 6/6.12/12 of masscomposition 6%/88%/6%, with an MFI at 235° C. under 5 kg of 5, a meltingpoint of 188° C. and a heat of fusion of 55 J/g.

PA 6/6.10/12 (6%/88%/6%) denotes a copolyamide 6/6.10/12 of masscomposition 6%/88%/6%, with an MFI at 235° C. under 5 kg of 8, a meltingpoint of 189° C. and a heat of fusion of 53 J/g.

PA 6/6.12/12 (85%/5%/10%) denotes a copolyamide 6/6.12/12 of masscomposition 85%/5%/10%, with an MFI at 235° C. under 5 kg of 6, amelting point of 189° C. and a heat of fusion of 55 J/g.

PA 6/6.12/12/10.10 denotes a copolyamide 6/6.12/12/10.10 of masscomposition 6%/88%/3%/3%, with an MFI at 235° C. under 5 kg of 6, amelting point of 186° C. and a heat of fusion of 50 J/g.

PA 6.T/6.12/12 (6%/88%/6%) denotes a copolyamide 6.T/6.12/12 of masscomposition 6%/88%/6%, with an MFI at 235° C. under 5 kg of 3.

Stab1 denotes a mixture of organic stabilizers consisting of 0.8% ofphenol Lowinox 44B25 from the company Great Lakes and of 0.2% ofphosphite Irgafos 168 from the company Ciba.

EPR1 denotes a copolymer of ethylene and propylene of elastomeric naturefunctionalized with a group that is reactive with an anhydride function(at 0.5-1% by mass), with an MFI of 9 (at 230° C., under 10 kg), ofExxellor VA1801 type from the company Exxon used as impact modifier. Itsflexural modulus is 10 MPa approximately according to standard ISO178.

Plasticizing or BBSA denotes benzyl butyl sulfonamide (BBSA). Thecomparative compositions given in Table 2 were prepared from thefollowing components.

PA 6/6.10/12 (20%/20%/60%) denotes a copolyamide 6/6.10/12 of masscomposition 20%/20%/60%, with an MFI at 235° C. under 5 kg of 5, amelting point of 128° C. and a heat of fusion of 23 J/g.

PA 6/6.10/12 (18%/58%/24%) denotes a copolyamide 6/6.10/12 of masscomposition 18%/58%/24%, with an MFI at 235° C. under 5 kg of 5, amelting point of 144° C. and a heat of fusion of 42 J/g.

PA 6/6.10/12 (60%/10%/30%) denotes a copolyamide 6/6.10/12 of masscomposition 60%/10%/30%, with an MFI at 235° C. under 5 kg of 6, amelting point of 149° C. and a heat of fusion of 42 J/g.

1.2 Formation of the Pipes

These compositions are then used as binder layer for a multilayer pipewith an outside diameter of 8 mm and an inside diameter of 6 mm.

These pipes 1 mm thick are constituted in the following manner:

Outer layer of PA12-TL of 450 μm//binder layer of 50 μm//inner layer ofPA6a.

The definitions of PA12-TL and PA6a are as follows:

PA6a denotes a composition based on polyamide 6 with an Mn(number-average molecular mass) of 28 000, containing 10% of plasticizerBBSA (benzyl butyl sulfonamide), 12% of functionalized EPR ExxelorVA1803 (from the company Exxon) and 1.2% of organic stabilizersconsisting of 0.8% of phenol (Lowinox 44B25 from the company GreatLakes), 0.2% of phosphite (lrgafos 168 from the company Ciba) and 0.2%of anti-UV agent (Tinuvin 312 from the company Ciba). The melting pointof this composition is 215° C.

PA12-TL denotes a composition based on polyamide 12 with an Mn(number-average molecular mass) of 35 000, containing 6% of plasticizerBBSA (benzyl butyl sulfonamide), 6% of anhydride-functionalized EPRExxelor VA1801 (from the company Exxon), and 1.2% of organic stabilizersconsisting of 0.8% of phenol (Lowinox 44B25 from the company GreatLakes), 0.2% of phosphite (lrgafos 168 from the company Ciba) and 0.2%of anti-UV agent (Tinuvin 312 from the company Ciba). The melting pointof this composition is 175° C.

1.3 Evaluation of the Pipes

The adhesion was measured on these multilayers before and afterimmersion in hot biofuel.

ADH1 Corresponds to the Measurement of the Adhesion Force Expressed inN/cm.

This is reflected by the measurement of the peel force, expressed inN/cm, and measured on the tube before it has been subjected to 15 daysof conditioning at 50% relative humidity at 23° C. The given valueconcerns the weakest interface, i.e. the interface that is the leastadherent of the multilayer, where there is the greatest risk ofdetachment. The peeling is performed at the interface by subjecting oneof the parts to traction at an angle of 90° and at a speed of 50 mm/min.

VG=very good, >80

G=good, between 80 and >60

QG=quite good (acceptable), between 60 and >30

P=poor, between 30 and 10

VP<10=very poor

ADH2 Corresponds to the Measurement of the Adhesion Force After the Testin Biofuel, Expressed in N/cm

Same test as for the measurement of ADH1 described above, except thatthe interior of the pipe is filled with a biofuel E50 at 80° C. for 200hours. The biofuel E50 is a mixture comprising by mass 50% of ethanol,44% of gasoline L, 5% of water and 1% of methanol according to standardB31 5220 from the company Peugeot SA, the gasoline known as “L” beingthe reference lead-free gasoline of the Euro standard, referenced underthe code E-H-003. These test conditions are much more severe than thepreceding ones. The assessment criteria take this into account and are:

G=good, >30

QG=quite good (acceptable), >20 to <=30

P=poor, >10 to <=20

VP=very poor, <=10

The results are given in Tables 1 and 2 below.

Table 1 comprises compositions 1 to 6 according to the invention.

TABLE 1 11 12 13 14 15 16 PA 6/6.12/12 100 89 — — — — (6%/88%/6%) PA6/6.10/12 — — 89 — — — (6%/88%/6%) PA 6/6.10/12 — — — 89 — —(85%/5%/10%) PA 6/6.12/12/10.10 — — — — — 89 (6%/88%/3%/3%) PA6.T/6.12/12 — — — — 89 — (6%/88%/6%) EPR1 — 10 — — 10 10 Plasticizer — —10 10 — — BBSA Stab1 — 1 1 1 1 1 Evaluation of the adhesion between theouter layer (made of PA12-TL) and inner layer (made of PA6a) of themultilayer pipe ADH1 58 65 61 33 61 66 ADH2 >30 >30 >30 >30 >30 >30

Table 2 comprises comparative compositions C1 to C3.

TABLE 2 C1 C2 C3 PA 6/6.10/12 89 — — (20%/20%/60%) PA 6/6.10/12 — 89 —(18%/58%/24%) PA 6/6.10/12 — — 89 (60%/10%/30%) EPR1 10 — — Plasticizer— 10 10 BBSA Stab1 1 1 1 Evaluation of the adhesion between the outerlayer (made of PA12-TL) and inner layer (made of PA6a) of the multilayerpipe ADH1 47 44 45 ADH2 <10 <10 <10

Compositions 1, 2, 3, 4, 5 and 6 give satisfactory results in terms ofadhesion between the layer of PA12 and the layer of PA6, when comparedwith the results obtained with the comparative compositions.

Specifically, it was observed that the adhesion (denoted ADH2) obtainedwith comparative compositions C1, C2 and C3 becomes insufficient aftercontact with biofuel gasoline.

2/When the Composition According to the Invention Comprises a Mixture ofTwo Copolyamides Consisting of Units A, B and C

2.1 Preparation of the Compositions

The compositions according to the invention given in Table 3 wereprepared from the following components. The amounts of products areexpressed as weight percentages relative to the total weight of thecomposition.

PA 6/6.12 (90%/10%) denotes a copolyamide 6/6.12 of mass composition90%/10%, with an MFI at 235° C. under 5 kg of 7, a melting point of 199°C. and a heat of fusion of 58 J/g.

PA 6.12/12 (10%/90%) denotes a copolyamide 6.12/12 of mass composition10%/90%, with an MFI at 235° C. under 5 kg of 7, a melting point of 163°C. and a heat of fusion of 38 J/g.

PA 6/6.12 (10%/90%) denotes a copolyamide 6/6.12 of mass composition10%/90%, with an MFI at 235° C. under 5 kg of 5, a melting point of 187°C. and a heat of fusion of 58 J/g.

PA 6.12/12 (90%/10%) denotes a copolyamide 6.12/12 of mass composition90%/10%, with an MFI at 235° C. under 5 kg of 6, a melting point of 185°C. and a heat of fusion of 52 J/g.

PA 10.T/10.10 (80/20%) denotes a copolyamide 10.T/10.10 of masscomposition 80/20%, with an inherent viscosity of 1.10, a melting pointTm of 292° C. and a heat of fusion of 49 J/g.

The comparative composition given in Table 3 was prepared from thefollowing components.

PA 6/6.12 (50%/50%) denotes a copolyamide 6/6.12 of mass composition50%/50%, with an MFI at 235° C. under 5 kg of 5, a melting point of 148°C. and a heat of fusion of 24 J/g.

PA 6.12/12 (50%/50%) denotes a copolyamide 6.12/12 of mass composition50%/50%, with an MFI at 235° C. under 5 kg of 4, a melting point of 143°C. and a heat of fusion of 24 J/g.

2.2 Formulations of the Pipes

These compositions are then used as binder layer for a multilayer pipewith an outside diameter of 8 mm and an inside diameter of 6 mm in amanner strictly similar to that of point 1.2.

2.3 Evaluation of the Pipes

The adhesion was measured on these multilayers before and afterimmersion in hot biofuel, in a manner strictly similar to that of point1.3.

The compositions and results are given in Table 3 below.

TABLE 3 21 22 23 24 25 C21 PA 6/6.12 44.5 50 — 50 — — (90%/10%) PA6.12/12 44.5 50 — — — — (10%/90%) PA 6/6.12 — — 50 — 60 — (10%/90%) PA6.12/12 — — 50 50 — — (90%/10%) PA 6/6.12 — — — — — 50 (50%/50%) PA10.T/10.10 — — — — 40 — (80%/20%) PA 6.12/12 — — — — — 50 (50%/50%) EPR110 — — — — — Stab1 1 — — — — — Evaluation of the adhesion between theouter layer (made of PA12-TL) and inner layer (made of PA6a) of themultilayer pipe ADH1 71 80 68 38 37 73 ADH2 >30 >30 >30 >30 >30 <10

Compositions 21, 22, 23, 24 and 25 give satisfactory results in terms ofadhesion between the layer of PA12 and the layer of PA6, when comparedwith the results obtained with comparative composition C21.

Specifically, it was observed that the adhesion (denoted ADH2) obtainedwith comparative composition C21 becomes insufficient after contact withthe hot biofuel gasoline.

3/When the Composition According to the Invention Comprises a Mixture ofa Copolyamide and of a Homopolyamide Consisting of Units A, B and C

3.1 Preparation of the Compositions

The compositions according to the invention given in Table 4 wereprepared from the following components. The amounts of products areexpressed as weight percentages relative to the total weight of thecomposition.

PA12 denotes polyamide 12 with an inherent viscosity of 1.65. Itsmelting point is 178° C. and its heat of fusion is 54 kJ/kg.

PA6 denotes a polyamide 6 of Mn (number-average molecular mass) 28 000.Its melting point is 220° C. and its heat of fusion is 68 kJ/kg.

The comparative compositions given in Table 5 were prepared from thefollowing components.

PA 6/12 (50%/50%) denotes a copolyamide 6/12 of mass composition50%/50%, with an MFI at 235° C. under 5 kg of 4, a melting point of 144°C. and a heat of fusion of 22 J/g.

PA6.12 denotes polyamide 6.12 of Mn (number-average molecular mass) 29000. Its melting point is 218° C. and its heat of fusion is 67 kJ/kg.

3.2 Formulations of the Pipes

These compositions are then used as binder layer for a multilayer pipewith an outside diameter of 8 mm and an inside diameter of 6 mm, in amanner strictly similar to that of point 1.2.

3.3 Evaluation of the Pipes

The adhesion was measured on these multilayers before and afterimmersion in hot biofuel, in a manner strictly similar to that of point1.3.

The compositions according to the invention and results are given inTable 4 below.

TABLE 4 31 32 33 34 PA 6/6.12 50 60 — — (90%/10%) PA 12 39 40 — 40 PA 6— — 50 — PA 6.12/12 — — 50 — (10%/90%) PA 6/6.12 — — — 60 (10%/90%) EPR110 — — — Stab1 1 — — — Evaluation of the adhesion between the outerlayer (made of PA12-TL) and inner layer (made of PA6a) of the multilayerpipe ADH1 49 46 46 40 ADH2 >30 >30 >30 >30

The comparative compositions and results are given in Table 5 below.

TABLE 5 Without binder C31 C32 PA 12 — 40 — PA 6/12 — 60 40 (50%/50%)PA6.12 — — 60 EPR1 — — — Stab1 — — — Evaluation of the adhesion betweenthe outer layer (made of PA12-TL) and inner layer (made of PA6a) of themultilayer pipe ADH1 <5 45 63 ADH2 <5 <10 <10

Compositions 31, 32, 33 and 34 give satisfactory results in terms ofadhesion between the layer of PA12 and the layer of PA6, when comparedwith the results obtained with the comparative compositions.

Specifically, it was observed that the adhesion (denoted ADH2) becomesinsufficient after contact with hot biofuel gasoline.

4/Various Comparative Examples

4.1 Preparation of the Comparative Compositions

The comparative compositions given in Table 6 were prepared from thefollowing components. The amounts of products are expressed as weightpercentages relative to the total weight of the composition.

PA6.10 denotes a polyamide 6.10 of Mn (number-average molecular mass) 30000 and having an excess of NH₂ amine chain ends relative to the COOHchain ends, the concentration of NH₂ chain ends being 45 μeq/g. Itsmelting point is 223° C. and its heat of fusion is 61 kJ/kg.

Binder coPA denotes a composition based on 50% copolyamide 6/12 (of30/70 mass ratio) of Mn 16 000, and 50% copolyamide 6/12 (of 70/30 massratio) of Mn 16 000.

Binder PPg denotes a composition based on PP (polypropylene) graftedwith maleic anhydride, known under the name Admer QF551A from thecompany Mitsui.

Binder PA6.10+PA6 denotes a composition based on PA6.10 obtained bypolycondensation of hexanediamine with decanedioic acid (of Mn 30 000,and as defined elsewhere) and 36% of PA6 (of Mn 28 000, and as definedelsewhere); the mass-weighted mean of the heats of fusion is 63.5 J/gand the heat of fusion of the PA6 is 220° C.; and 1.2% of organicstabilizers (consisting of 0.8% of phenol Lowinox 44B25 from the companyGreat Lakes, 0.2% of phosphite lrgafos 168 from the company Ciba and0.2% of anti-UV agent Tinuvin 312 from the company Ciba).

Binder PA6.12+PA6 denotes a composition based on PA6.12 obtained bypolycondensation of hexanediamine with dodecanedioic acid (of Mn 29 000,and as defined elsewhere) and 36% of PA6 (of Mn 28 000, and as definedelsewhere) and 1.2% of organic stabilizers (consisting of 0.8% of phenolLowinox 44B25 from the company Great Lakes, 0.2% of phosphite lrgafos168 from the company Ciba and 0.2% of anti-UV agent Tinuvin 312 from thecompany Ciba).

Binder PA6.10+PA12 denotes a composition based on PA6.10 obtained bypolycondensation of hexanediamine with decanedioic acid (of Mn 30 000,and as defined elsewhere) and 36% of PA12 (of Mn 35 000, and as definedelsewhere) and 1.2% of organic stabilizers (consisting of 0.8% of phenolLowinox 44B25 from the company Great Lakes, 0.2% of phosphite lrgafos168 from the company Ciba and 0.2% of anti-UV agent Tinuvin 312 from thecompany Ciba).

Binder PA6+PA12+imod denotes a composition based on 40% PA6 (of Mn 28000), 40% of PA12 (of Mn) and 20% of functionalized EPR Exxelor VA1801(from the company Exxon) and 1.2% of organic stabilizers (consisting of0.8% of phenol Lowinox 44B25 from the company Great Lakes, 0.2% ofphosphite Irgafos 168 from the company Ciba and 0.2% of anti-UV agentTinuvin 312 from the company Ciba).

PA6.12 denotes polyamide 6.12 obtained by polycondensation ofhexanediamine with dodecanedioic acid of Mn (number-average molecularmass) 29 000. Its melting point is 218° C. and its heat of fusion is 67kJ/kg.

4.2 Formulations of the Pipes

These compositions are then used as binder layer for a multilayer pipewith an outside diameter of 8 mm and an inside diameter of 6 mm, in amanner strictly similar to that of point 1.2.

4.3 Evaluation of the Pipes

The adhesion was measured on these multilayers before and afterimmersion in hot biofuel, in a manner strictly similar to that of point1.3.

The comparative compositions and results are given in Table 6 below.

TABLE 6 C41 C42 C43 C44 C45 C46 C47 Binder coPA 100 — — — — — — BinderPPg — 100 — — — — — Binder PA6.10 + — — 100 — — — — PA6 Binder PA6.12 +— — — 100 — — — PA6 Binder PA6.10 + — — — — 100 — — PA12 Binder PA6 +PA12 + — — — — — 100 — imod PA6.12 — — — — — — 100 Evaluation of theadhesion between the outer layer (made of PA12-TL) and inner layer (madeof PA6a) of the multilayer pipe ADH1 >60 >60 26 28 29 22 18 ADH2 <10 <1014 16 18 20 11

5/Use of the Compositions as Binder for Other Types of MultilayerStructure Based on Polyphthalamide

5.1 Preparation of the Compositions

The compositions used are those described above.

5.2 Formulations of the Pipes

These compositions are then used as binder layer for a multilayer pipewith an outside diameter of 8 mm and an inside diameter of 6 mm.

The multilayer structure of these examples is of the following nature:outer layer of PA12-TL of 450 μm//binder layer of 50 μm//inner layer ofPPAb.

The purpose of the binder here is to afford adhesion between the PA12layer and the layer of polyphthalamide of 6.T/6 type, since the latterdo not naturally adhere to each other.

PPAb denotes a composition based on polyphthalamide of copolyamide 6.T/6type Ultramid TKR4351 from the company BASF, and 25% of functionalizedEPR Exxelor VA1803 (from the company Exxon), and 0.5% of stabilizerbased on copper and potassium iodide of Iodide P201 type (from thecompany Ciba). The melting point of this composition is 295° C.

5.3 Evaluation of the Pipes

The adhesion was measured on these multilayers before and afterimmersion in hot biofuel, in a manner strictly similar to that of point1.3.

The compositions according to the invention and comparative compositionsand the results are given in Table 7 below.

TABLE 7 11 12 21 31 C11 PA 6/6.12/12 100 89 — — — (6%/88%/6%) PA 6/6.12— — 44.5 50 — (90%/10%) PA 6.12/12 — — 44.5 — — (10%/90%) PA 12 — — — 39— PA 6/6.10/12 — — — — 89 (20%/20%/60%) EPR1 — 10 10 10 10 Stab1 — 1 1 11 Evaluation of the adhesion between the outer layer (made of PA12- TL)and inner layer (made of polyphthalamide PPAb) of the multilayer pipeADH1 55 68 65 51 49 ADH2 >30 >30 >30 >30 <10

It is found that good adhesion values are also obtained between thelayer of PA12 and the layer of polyphthalamide of PA6.T/6 type,especially after exposure to biofuel, in contrast with the comparativeexamples.

6/Use of the Compositions as Binder for Other Types of MultilayerStructure Based on EVOH

6.1 Preparation of the Compositions

The compositions used are those described above.

6.2 Formulations of the Pipes

These compositions are then used as binder layer for a multilayer pipewith an outside diameter of 8 mm and an inside diameter of 6 mm. Thepipes are made by coextrusion of the compositions in the melt, i.e.above their melting point.

The multilayer structure of these examples is now of the followingnature: outer layer of PA12-TL of 425 μm//binder layer of 50 μm//layerof EVOH of 100 μm//inner layer of PA6a of 425 μm.

The purpose of the binder here is to afford adhesion between the PA12layer and the EVOH layer, since the latter do not naturally adhere toeach other.

EVOH denotes a copolymer of ethylene vinyl alcohol, for example SoarnolDC3203RB from the company Nippon Gosei. The melting point of thiscomposition is 183° C.

6.3 Evaluation of the Pipes

The adhesion was measured on these multilayers before and afterimmersion in hot biofuel, in a manner strictly similar to that of point1.3.

The compositions according to the invention and comparative compositionsand the results are given in Table 8 below.

11 12 21 31 C13 C21 C31 PA 6/6.12/12 100 89 — — — — — (6%/88%/6%) PA6/6.12 — — 44.5 50 — — — (90%/10%) PA 6.12/12 — — 44.5 — — — — (10%/90%)PA 12 — — — 39 — — 40 PA 6/6.10/12 — — — — 89 — — (60%/10%/30%) PA6/6.12 — — — — 50 — (50%/50%) PA 6.12/12 — — — — — 50 — (50%/50%) PA6/12 — — — — — — 60 EPR1 — 10 10 10 — — BBSA — — — — 10 — — Stab1 — 1 11 1 — — Evaluation of the adhesion between the outer layer (made ofPA12-TL) and the EVOH layer of the multilayer pipe ADH1 44 49 59 50 7064 42 ADH2 >30 >30 >30 >30 <10 <10 <10

It is observed that good adhesion values are also obtained between thelayer of PA12 and the layer of EVOH, especially after exposure tobiofuel, in contrast with the comparative examples.

7/Example of a Process for Manufacturing Multilayer Structures: in theCase of Pipes

Multilayer pipes are made by coextrusion. A McNeil multilayer extrusionindustrial line is used, equipped with 5 extruders connected to amultilayer extrusion head with spiral mandrels.

The screws used are single extrusion screws having screw profilesadapted to the polyamides. In addition to the 5 extruders and themultilayer extrusion head, the extrusion line comprises:

a die-punch assembly, located at the end of the coextrusion head; theinside diameter of the die and the outside diameter of the punch arechosen as a function of the structure to be made and of the materials ofwhich it is composed, and also as a function of dimensions of the pipeand of the line speed;

a vacuum tank with an adjustable level of vacuum. In this tankcirculates water maintained in general at 20° C., into which is immerseda gauge for conforming the pipe to its final dimensions. The diameter ofthe gauge is adapted to the dimensions of the pipe to be made, typicallyfrom 8.5 to 10 mm for a pipe with an outside diameter of 8 mm and athickness of 1 mm;

a succession of cooling tanks in which water is maintained at about 20°C., for cooling the pipe along the path from the drawing head to thedrawing bench;

a diameter measurer;

a drawing bench.

The configuration with 5 extruders is used to make pipes ranging from 2layers to 5 layers. In the case of the structures in which the number oflayers is less than 5, several extruders are then fed with the samematerial.

EMBODIMENTS

1. An adhesive composition predominantly comprising one or twopolyamides consisting of units chosen from:

at least one unit denoted A with a mean number of carbon atoms pernitrogen atom, denoted C_(A), ranging from 4 to 8.5, advantageously from4 to 7;

at least one unit denoted B with a mean number of carbon atoms pernitrogen atom, denoted C_(B), ranging from 7 to 10, advantageously from7.5 to 9.5;

at least one unit denoted C with a mean number of carbon atoms pernitrogen atom, denoted C_(C), ranging from 9 to 18, advantageously from10 to 18; and

optionally at least one unit Z other than an amide unit;

the three units A, B and C being present in said polyamide or togetherin said polyamides;

one of the units A, B or C being in a very predominant proportion in thecopolyamide(s) and representing from 80% to 97% by weight relative tothe total weight of the copolyamide,

the mean number of carbon atoms per nitrogen atom of the units A, B andC also corresponding to the following strict inequality:C_(A)<C_(B)<C_(C),

the heat of fusion of the polyamide or the mass-weighted mean of theheats of fusion of the mixture of polyamides in said composition beinggreater than 25 J/g (DSC),

the melting point of the or of each of the polyamides being greater than150° C. (DSC).

2. The composition of embodiment 1, characterized in that the differencebetween mean numbers of carbon atoms per nitrogen atom (C_(B)-C_(A))and/or (C_(C)-C_(B)) ranges from 1 to 4 and preferably from 2 to 3.

3. The composition of embodiment 1 or 2, characterized in that thepolyamide or the two polyamides denote(s) a terpolyamide, ahomopolyamide combined with a copolyamide or two copolyamides.

4. The composition of embodiment 3, characterized in that the polyamideis a terpolyamide consisting of units A, B and C as defined inembodiment 1 or 2.

5. The composition of embodiment 3, characterized in that it comprises amixture of two different copolyamides each consisting of two unitschosen from units A, B and C as defined in embodiment 1 or 2.

6. The composition of embodiment 3, characterized in that it comprises amixture of a copolyamide consisting of two units chosen from units A, Band C and of a homopolyamide consisting of the third unit A, B or C,which is absent from the structure of the copolyamide, units A, B and Cbeing as defined in embodiment 1 or 2.

7. The composition of embodiment 6, characterized in that the meltingpoint of the homopolyamide consisting of unit A is greater than or equalto 210° C. and the melting point of the homopolyamide consisting of unitC is less than 200° C.

8. The composition of any one of the preceding embodiments,characterized in that

the amide unit A is chosen from units derived from the followingmonomers: 6, 4.6, 6.6, 6.T, 9.T and 9′.T, 9′ denoting2-methyl-1,8-octanediamine, i.e. the isomer of diamine-9 or1,9-nonanediamine;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, 9.T and 9′.T, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 6.18, 10.T, 12.T, 12/10.T, 12.12 and10.10/10.T.

9. The composition of the preceding embodiment, characterized in that

the amide unit A is chosen from units derived from the followingmonomers: 6, 4.6 and 6.6;

the amide unit B is chosen from units derived from the followingmonomers: 6.10, 6.12, preferably 6.10, and

the amide unit C is chosen from units derived from the followingmonomers: 10.10, 11, 12, 10.12, 12.12 and 6.18.

10. The use of the adhesive composition as defined in any one of thepreceding embodiments for making structures for transferring and/orstoring fluid, in particular a fluid chosen from an oil, a brake liquid,a cooling liquid, a urea solution, a hydrocarbon, a diesel, a gasoline,in particular a gasoline comprising a high proportion of alcohols,compressed air.

11. A structure comprising at least two layers, one of the two layers,referred to as the adhesive layer (I), being formed from an adhesivecomposition as defined in any one of embodiments 1 to 9.

12. The structure of embodiment 11, characterized in that the secondlayer, referred to as the barrier layer (II), is formed from acomposition comprising at least one polymer that is a barrier tobiofuels, preferably chosen from EVOH, a weakly-carbonic polyamide, anda mixture thereof.

13. The structure of embodiment 11 or 12, characterized in that thestructure comprises at least a third layer, referred to as thelong-lasting layer (III), formed from a composition comprising ahigh-carbon polyamide, this polyamide preferably being chosen from PA11,PA12, PA10.10, PA10.12, PA12/10.T, PA10.10/10.T and mixtures thereof,the adhesive layer (I) being arranged between said long-lasting layer(III) and the barrier layer (II) and adhering to the respective zone ofcontact thereof.

14. The structure of any one of embodiments 11 to 13, characterized inthat it is in the form of a pipe, a container, a film or a plate.

15. The use of a structure as defined in any one of embodiments 11 to14, especially when it is in the form of a pipe, for transporting andstoring fluids, especially present in vehicles.

16. The use of embodiment 15, characterized in that the fluid is chosenfrom an oil, a brake liquid, a urea solution, a glycol-based coolingliquid, fuels, and especially biofuels, and compressed air.

17. A polyamide consisting of the following units:

at least one unit denoted A with a mean number of carbon atoms pernitrogen atom, denoted C_(A), ranging from 4 to 8.5, advantageously from4 to 7;

at least one unit denoted B with a mean number of carbon atoms pernitrogen atom, denoted C_(B), ranging from 7 to 10, advantageously from7.5 to 9.5; and

at least one unit denoted C with a mean number of carbon atoms pernitrogen atom, denoted C_(C), ranging from 9 to 18, advantageously from10 to 18;

optionally at least one unit Z other than an amide unit;

one of the units A, B or C being in very predominant proportion in thepolyamide and representing from 80% to 97% by weight relative to thetotal weight of the polyamide,

the mean number of carbon atoms per nitrogen atom of the units A, B andC also corresponding to the following strict inequality: C_(A) <C_(B)<C_(C),

the heat of fusion of the polyamide being greater than 25 J/g (DSC),

the heat of fusion of the polyamide being greater than 150° C. (DSC).

18. The polyamide of embodiment 17, characterized in that it consists ofonly one unit A, only one unit B and only one unit C.

19. The polyamide of embodiment 17 or 18, characterized in that unit Bis the very predominant unit in the polyamide.

1. (canceled)
 2. An adhesive composition predominantly comprising apolyamide composition consisting of two polyamides, wherein at least onepolyamide is a copolyamide, the polyamide composition consisting ofunits chosen from: at least one amide unit denoted A (amide unit A) witha mean number of carbon atoms per nitrogen atom, denoted CA, rangingfrom 4 to 8.5; at least one amide unit denoted B (amide unit B) with amean number of carbon atoms per nitrogen atom, denoted CB, ranging from7 to 10; at least one amide unit denoted C (amide unit C) with a meannumber of carbon atoms per nitrogen atom, denoted CC, ranging from 9 to18; and optionally at least one unit Z other than an amide unit; thethree units A, B and C being present together in said two polyamides;one of the units A, B or C being in a very predominant proportion in thecopolyamide and representing from 80% to 97% by weight relative to thetotal weight of the copolyamide, the mean number of carbon atoms pernitrogen atom of the units A, B and C also corresponding to thefollowing strict inequality: CA<CB<CC, the mass-weighted mean of theheats of fusion of the polyamide composition being greater than 25 J/g(DSC), the melting point of each of the polyamides being greater than150° C. (DSC).
 3. The composition as claimed in claim 2, wherein thedifference between mean numbers of carbon atoms per nitrogen atom(CB-CA) and/or (CC-CB) ranges from 1 to
 4. 4. The composition as claimedin claim 2, wherein the two polyamides denote a homopolyamide combinedwith a copolyamide.
 5. The composition as claimed in claim 4, whereinthe polyamide composition is a mixture of a copolyamide consisting oftwo units chosen from units A, B and C and of a homopolyamide consistingof the third unit A, B or C, which is absent from the structure of thecopolyamide.
 6. The composition as claimed in claim 5, wherein thehomopolyamide is of unit A and the melting point of the homopolyamide isgreater than or equal to 210° C.; or wherein the homopolyamide is ofunit C and the melting point of the homopolyamide is less than 200° C.7. The composition as claimed in claim 2, wherein the two polyamidesdenote two copolyamides.
 8. The composition as claimed in claim 7,wherein the polyamide composition is a mixture of two differentcopolyamides each consisting of two units chosen from units A, B and C.9. The composition as claimed in claim 2, wherein the amide unit A ischosen from units derived from the following monomers: 6, 4.6, 6.6, 6.T,9.T and 9′.T, 9′ denoting 2 methyl-1,8-octanediamine; the amide unit Bis chosen from units derived from the following monomers: 6.10, 6.12,9.T and 9′.T, and the amide unit C is chosen from units derived from thefollowing monomers: 10.10, 11, 12, 10.12, 6.18, 10.T, 12.T, 12/10.T,12.12 and 10.10/10.T.
 10. The composition as claimed in claim 2, whereinthe amide unit A is chosen from units derived from the followingmonomers: 6, 4.6 and 6.6; the amide unit B is chosen from units derivedfrom the following monomers: 6.10, 6.12, and the amide unit C is chosenfrom units derived from the following monomers: 10.10, 11, 12, 10.12,12.12 and 6.18.
 11. A structure comprising at least a first layer and asecond layer, wherein the first layer is an adhesive layer (I) formedfrom the adhesive composition as defined in claim
 2. 12. The structureas claimed in claim 11, wherein the structure is in the form of a pipe,a container, a film or a plate.
 13. The structure as claimed in claim11, wherein the second layer is a barrier layer (II) formed from acomposition comprising at least one polymer that is a barrier tobiofuels, chosen from EVOH, a weakly-carbonic polyamide, and a mixturethereof.
 14. The structure as claimed in claim 13, wherein the structurecomprises at least a third layer, the third layer is a long-lastinglayer (III) formed from a composition comprising a high-carbonpolyamide, the adhesive layer (I) being arranged between saidlong-lasting layer (III) and the barrier layer (II) and adhering to therespective zone of contact thereof.
 15. The structure as claimed inclaim 11, wherein the second layer is a barrier layer (II), wherein thestructure comprises at least a third layer, the third layer is along-lasting layer (III) formed from a composition comprising ahigh-carbon polyamide, the adhesive layer (I) being arranged betweensaid long-lasting layer (III) and the barrier layer (II) and adhering tothe respective zone of contact thereof.
 16. A method for transporting orstoring a fluid, the method comprising transporting or storing a fluidin a structure as defined in claim 11, in the form of a pipe.
 17. Themethod as claimed in claim 16, wherein the fluid is chosen from an oil,a brake liquid, a urea solution, a glycol-based cooling liquid, fuels,and compressed air.